3 files changed, 259 insertions, 0 deletions
diff --git a/gui/widget/concurrent_face.go b/gui/widget/concurrent_face.go
new file mode 100644
index 0000000..98db572
--- /dev/null
+++ b/gui/widget/concurrent_face.go
@@ -0,0 +1,51 @@
+package widget
+
+import (
+	"image"
+	"sync"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+type concurrentFace struct {
+	mu   sync.Mutex
+	face font.Face
+}
+
+func (cf *concurrentFace) Close() error {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Close()
+}
+
+func (cf *concurrentFace) Glyph(dot fixed.Point26_6, r rune) (
+	dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Glyph(dot, r)
+}
+
+func (cf *concurrentFace) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphBounds(r)
+}
+
+func (cf *concurrentFace) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphAdvance(r)
+}
+
+func (cf *concurrentFace) Kern(r0, r1 rune) fixed.Int26_6 {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Kern(r0, r1)
+}
+
+func (cf *concurrentFace) Metrics() font.Metrics {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Metrics()
+}
diff --git a/gui/widget/text.go b/gui/widget/text.go
new file mode 100644
index 0000000..1b40096
--- /dev/null
+++ b/gui/widget/text.go
@@ -0,0 +1,78 @@
+package widget
+
+import (
+	"log"
+	"sync"
+
+	"image"
+	"image/color"
+	"image/draw"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/gofont/goregular"
+	"golang.org/x/image/font/opentype"
+	"golang.org/x/image/math/fixed"
+)
+
+var (
+	FONT      = goregular.TTF
+	FONT_SIZE = 15
+	DPI       = 72
+	PAD       = 3
+)
+
+var face *concurrentFace
+
+func init() {
+	fnt, err := opentype.Parse(FONT)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fce, err := opentype.NewFace(fnt, &opentype.FaceOptions{
+		Size: float64(FONT_SIZE),
+		DPI:  float64(DPI),
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	face = &concurrentFace{sync.Mutex{}, fce}
+}
+
+func TextSize(text string) image.Point {
+	bounds := textBounds([]byte(text), font.Drawer{Face: face})
+	return image.Point{bounds.Max.X - bounds.Min.X + 2*PAD, bounds.Max.Y - bounds.Min.Y + 2*PAD}
+}
+
+func drawText(text []byte, dst draw.Image, r image.Rectangle, fg, bg color.Color) {
+	drawer := font.Drawer{
+		Src:  &image.Uniform{fg},
+		Face: face,
+		Dot:  fixed.P(0, 0),
+	}
+
+	// background
+	draw.Draw(dst, r, &image.Uniform{bg}, image.ZP, draw.Src)
+
+	// text image
+	bounds := textBounds(text, drawer)
+	textImg := image.NewRGBA(bounds)
+	draw.Draw(textImg, bounds, &image.Uniform{bg}, image.ZP, draw.Src)
+	drawer.Dst = textImg
+	drawer.DrawBytes(text)
+
+	// draw text image over background
+	leftCentre := image.Pt(bounds.Min.X, (bounds.Min.Y+bounds.Max.Y)/2)
+	target := image.Pt(r.Max.X-bounds.Max.X-PAD, (r.Min.Y+r.Max.Y)/2)
+	delta := target.Sub(leftCentre)
+	draw.Draw(dst, bounds.Add(delta).Intersect(r), drawer.Dst, bounds.Min, draw.Src)
+}
+
+func textBounds(text []byte, drawer font.Drawer) image.Rectangle {
+	b, _ := drawer.BoundBytes(text)
+	return image.Rect(
+		b.Min.X.Floor(),
+		b.Min.Y.Floor(),
+		b.Max.X.Ceil(),
+		b.Max.Y.Ceil(),
+	)
+}
diff --git a/gui/widget/widget.go b/gui/widget/widget.go
new file mode 100644
index 0000000..cbc837e
--- /dev/null
+++ b/gui/widget/widget.go
@@ -0,0 +1,130 @@
+package widget
+
+import (
+	"cmp"
+	"fmt"
+
+	"image"
+	"image/color"
+	"image/draw"
+
+	"volute/gui"
+	"volute/gui/win"
+)
+
+var (
+	FOCUS_COLOR = color.RGBA{179, 217, 255, 255}
+	GREEN       = color.RGBA{51, 102, 0, 255}
+	BLACK       = color.Gray{0}
+	WHITE       = color.Gray{255}
+)
+
+func Label(text string, r image.Rectangle, env gui.Env) {
+	redraw := func(drw draw.Image) image.Rectangle {
+		drawText([]byte(text), drw, r, BLACK, WHITE)
+		return r
+	}
+	env.Draw() <- redraw
+	for event := range env.Events() {
+		switch event := event.(type) {
+		case win.WiFocus:
+			if event.Focused {
+				env.Draw() <- redraw
+			}
+		}
+	}
+	close(env.Draw())
+}
+
+func Input(val chan<- uint, r image.Rectangle, focusChan <-chan bool, env gui.Env) {
+	redraw := func(text []byte, focus bool) func(draw.Image) image.Rectangle {
+		return func(drw draw.Image) image.Rectangle {
+			if focus {
+				drawText(text, drw, r, GREEN, FOCUS_COLOR)
+			} else {
+				drawText(text, drw, r, GREEN, WHITE)
+			}
+			return r
+		}
+	}
+	text := []byte{'0'}
+	focus := false
+
+	env.Draw() <- redraw(text, focus)
+
+	for {
+		select {
+		case focus = <-focusChan:
+			env.Draw() <- redraw(text, focus)
+		case event := <-env.Events():
+			switch event := event.(type) {
+			case win.WiFocus:
+				if event.Focused {
+					env.Draw() <- redraw(text, focus)
+				}
+			case win.KbType:
+				if focus && isDigit(event.Rune) {
+					text = fmt.Appendf(text, "%c", event.Rune)
+					env.Draw() <- redraw(text, focus)
+					val <- atoi(text)
+				}
+			case win.KbDown:
+				if focus && event.Key == win.KeyBackspace && len(text) > 0 {
+					text = text[:len(text)-1]
+					env.Draw() <- redraw(text, focus)
+					val <- atoi(text)
+				}
+			}
+		}
+	}
+	close(env.Draw())
+}
+
+func Output(val <-chan uint, r image.Rectangle, env gui.Env) {
+	redraw := func(n uint) func(draw.Image) image.Rectangle {
+		return func(drw draw.Image) image.Rectangle {
+			drawText([]byte(fmt.Sprint(n)), drw, r, BLACK, WHITE)
+			return r
+		}
+	}
+
+	var n uint = 0
+	env.Draw() <- redraw(n)
+
+Loop:
+	for {
+		select {
+		case n = <-val:
+			env.Draw() <- redraw(n)
+		case event, ok := <-env.Events():
+			if !ok { // channel closed
+				break Loop
+			}
+			if event, ok := event.(win.WiFocus); ok && event.Focused {
+				env.Draw() <- redraw(n)
+			}
+		}
+	}
+	close(env.Draw())
+}
+
+func isDigit(r rune) bool {
+	return '0' <= r && r <= '9'
+}
+
+func contains[T cmp.Ordered](slc []T, v T) bool {
+	for i := range slc {
+		if slc[i] == v {
+			return true
+		}
+	}
+	return false
+}
+
+func atoi(s []byte) uint {
+	var n uint = 0
+	for _, d := range s {
+		n = n*10 + uint(d-'0')
+	}
+	return n
+}